Warner Bros. has become the second studio to support both high definition DVD formats, a move that could shift the advantage to the Blu-ray format (search) backed by a group led by Sony Corp.

Warner Bros. Entertainment said Thursday it would join the board of the Blu-ray Disc Association and will release its films on both the Blu-ray and the rival HD DVD (search) format, which is backed by a group led by Toshiba Corp.

Earlier this month, Paramount Pictures, another supporter of HD DVD, said it would release films in both formats.

The move comes the day after Hewlett-Packard Co., a major backer of Blu-ray, urged that it be more consumer-friendly in a bid to forestall a lengthy and costly war with a competing standard.

Last month, the six major studios were evenly split between support of the two rival formats.

After Thursday, NBC Universal is the only company that has said it will release films in the HD DVD format only. None of the three early backers of Blu-ray, including The Walt Disney Co., have said they will release their films in HD DVD.

Warner Bros. said it decided to join the Blu-ray board after becoming convinced that a costly and confusing format war (search) could not be avoided.

"We think there will be a format war," said Jim Cardwell, president of Warner Home Video.

"We are going to put our product on for consumers on both formats," said Marsha King, executive vice president of New Business Development at Warner Home Video. "The market will decide if the functionality, if the price, if the consumer offering is what they want."

But Disney and Twentieth Century Fox hailed the Warner Bros. announcement Thursday, saying it would strengthen Blu-ray and avoid a costly competition.

"The continued dramatic momentum toward Blu-ray makes us more optimistic than ever that a format war can be avoided," said Bob Chapek, president of Buena Vista Home Entertainment.

Warner Bros. said that by joining the Blu-ray Disc Association, it could more strongly influence the cost of making the discs and consumer features, including the ability to copy DVDs onto a home network.

But if both formats hit the market early next year as planned, consumers may avoid high definition DVD for years, delaying the adoption of either format and ultimately hurting the studios, which make the majority of their profit from the sale of home video.

In a statement late Thursday, Toshiba said Warner Bros.' decision to join the Blu-ray group "represents the studio's understandable commitment to listen to a broad array of opinions and to continue to make technical evaluations of each format, and we are more than confident this will not affect timely introduction of HD DVD content to the market."

A study released Wednesday by Forrester Research concluded that the Blu-ray format will win, but that unless the rival HD DVD group abandons the field, it will be at least two years before consumers feel comfortable enough to buy a new format DVD player.

"The war between Betamax (search) and VHS (search) trained a generation of consumers to be wary of competing formats," the Forrester report said. "So, until a winner is very clear, only the most adventurous movie lovers will invest in high definition DVD players and discs."

Sony has said it will put Blu-ray discs on its PlayStation 3 (search) game console, a move that will potentially get the new format into thousands of homes.

Microsoft Corp., which backs HD DVD, has not said if its new XBox (search) game console will support the HD DVD format.